Ant Colony System Based Control Channel Selection Scheme for Guaranteed Rendezvous in Cognitive Radio Ad-hoc Network

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Ant Colony System Based Control Channel Selection Scheme for Guaranteed Rendezvous in

Cognitive Radio Ad-hoc Network

Henry Ohize^∗ and Mqhele Dlodlo^† Department of Electrical Engineering,

University of Cape Town Cape Town, South Africa

Email:^∗ [email protected], ^† [email protected]

Abstract—Achieving fast Time to Rendezvous (TTR) on a common coordination channel in an Ad-hoc network remains a contemporary issue in Cognitive Radio (CR) research. In this paper, we present a new channel hopping algorithm for the selection of a control channel in a heterogeneous, spatial, and time varying spectrum environment, with no pre-existing infrastructure such as an access point or a base station. We adopt the use of the bio-mimicry concept to develop a swarm intelligencebasedmechanism,whichwillguidenodesseekingto initiate communication, in selecting a common control channel within a boundedtime. Closed form expressionsfor the upper bound of TTR and Expected TTR (ETTR) were derived for various network scenarios. We provide a theoretical analysis of the TTR and ETTR of our algorithm, and show that our algorithmprovidesaTTRwithinorderO(M)ascomparedwith GeneratedOrthogonalSequence(GOS)andChannelRendezvous Sequence (CRSEQ) of order O(P²). The algorithm further providesan improvedperformanceincomparison totheJump- StayandEnhancedJump-StayRendezvousAlgorithms.Wealso provided simulation results to validate our claim of improved TTR.

I. INTRODUCTION

Severalspectrumsurveysconductedacrosstheglobereveal spectrum under-utilization as opposedto scarcity. The major cause of this pseudo scarcity of spectrum is the current paradigm of allocation technique known as the ”Command andControlTechnique(CCT)”.CCTisexposedtolimitation, as everyradiotechnologymusthaveapredefinedanddistinct spectrumforcommunication.CCThasfailedtoidentifyunder- utilized bands.The trendingsolutionis theuseof unlicensed devices bysecondaryusers(SU)intheseunderutilizedbands opportunistically. The Federal Communication Commission (FCC)recentlyadoptedthissolution.Theenablingtechnology for opportunisticspectrumusageistheCognitive Radio(CR) technology.

CR,isdefineda sar adioc apableo fi dentifyingi tsspectral environment and able to optimally adjust its transmission parameters to achieve an interference-free communication channel.InCRtechnology,DynamicSpectrumAccess(DSA) is made feasible. However, spectrumaccess by opportunistic user(SU)inCRmustavoidco-tierandcross-tierinterference,

accurately detect spectrum and make decisions, and guarantee Quality of Service.

Several MAC protocol design schemes have been proposed to suit multichannel CR network for centralized architectures such as IEEE 802.22 and Dynamic Spectrum Access Protocol.

However, few have been designed for distributed network also known as Ad-Hoc Network. Ad-Hoc network has zero form factor due to the absence of a central coordinator such as an access point or a base station, this has added to the complexity of developing a suitable MAC for CRAHN in addition to CRs spectrum heterogeneity, spatial and time varying spectrum availability [1]. The introduction of fixed or preselected common control channel (CCC) in MAC protocol design has remained the favourite solution in most works, however, this technique leaves more to be desired. The fixed CCC is exposed to control channel jamming, coverage limitations and it is not always robust to PU activities. To this day the most favoured solution is the implementation of a dynamic CCC (DCCC) for CRAHN [2] [3]. DCCC facilitates a variety of operations from transmitter-receiver handshake, neighbour discovery, channel access negotiation, topology change and routing information updates, to the cooperation among CR users. DCCC in some text is implemented as channel hopping technique [4].

In this work, we develop an Ant Colony System (ACS) based control channel selection scheme. By ACS we make reference to the mimicry of pheromone laying behaviour of real ants to find the shortest route between their nest and a food source. ACS technique is popular in literature as Ant Colony optimization. In this paper, we construct a channel hopping algorithm which will reinforce channels with best characteristics in the solution pool for selection as our control channel. We showed that by employing our algorithm we have improved on time to rendezvous. By rendezvous, we refer to the process of convergence which occurs when each SU node seeking to communicate with another must first converge on a common channel to establish a link.

The concept of node convergence on a common channel in CR networks has gained tremendous attention in recent years. Channel hopping (CH) is one such technique where communicating CR nodes hop across different available bands.

2016 IEEE 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications - (PIMRC): MAC &

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